Facile fabrication of Fe3O4@UiO-66-NH2/popcorn-like gold nanoparticles based SERS substrate for selective enrichment and real-time detection of residual enrofloxacin in milk

In this study, a magnetic metal-organic frameworks (MOFs) based hybrid substrate was designed and fabricated for SERS detection of enrofloxacin (ENR) in milk. The magnetic MOF (Fe 3 O 4 @UiO-66-NH 2 ) was synthesized by a facile microwave-assisted method, then loaded with popcorn-like Au nanoparticles (NPs) through electrostatic interaction. The as-prepared SERS substrate (Fe 3 O 4 @UiO-66-NH 2 /Au NPs) integrated the abundant hot spots of popcorn-like Au NPs with porous Fe 3 O 4 @UiO-66-NH 2 , which greatly improved its SERS activity and stability. More importantly, benefiting from the fingerprint characteristics of SERS and adsorption performance of Fe 3 O 4 @UiO-66-NH 2 , the SERS substrate exhibited high selectivity and sensitivity in detecting ENR. Under the optimal detection condition, a good linearity (R 2  = 0.996) was obtained with ENR concentration of 1.0 × 10 −9 –1.0 × 10 −6  M in spiked milk, the LOD was as low as 5.26 × 10 −10  M, and the recoveries were in the range of 76.1–86.1 % at three different spiking levels. The whole detection process including sample pretreatment took about 50 min, which indicating that the prepared substrate has great potential in sensitive and real-time detection of ENR in milk.